Means and apparatus for producing high vacuums.



No. 859,021. PATENTED JULY 2, 1907.

P. SODDY. v MEANS AND APPARATUS FOR PRODUCING HIGH VAGUUMS.

APPLICATION FILED JULY13.190B.

5 SHEETS-SHEET 1.

. "wrrmzsszs INIV'ENTOR Ewzg g V MWJM PATENTED JULY 2, 1907. P. SODDY.MEANS AND APPARATUS FOR PRODUCING HIGH VAGUUMS.

APPLICATION FILED JHLY13, 1906.

5 SHEETBSHBET Z.

INVENTOR 3W WITNESSE iATENTED JULY 2, 1907.

F. SODDY. MEANS AND APPARATUS FOR PRODUGING HIGH VAGUUMS.

APPLIUATIOH FILED JULY 13. 1906.

6 SHEETS-SHEET 3.

WITNESSES No. 859,021. PATENTED JULY 2, 1907. P. SUDDY. MEANS ANDAPPARATUS FOR PRODUCING HIGH VAGUUMS.

APPLICATION FILED JULY 13, 1906.

5 SHEETS-SHEET 4.

3 B M W Jr P .N 6' .M M

wrrmzsszs IN'VEINTOR PATENTED JULY 2, 1907.

F. SODDY. MEANS AND APPARATUS FOR PRODUCING HIGH VAGUUMS.

APPLIOATION FILED JULY 13. 1906.

5 SHEETS-SHEET 5.

"INIIHIII WITN 25's :5 MM M IIH IIIHI! HI! HI ll" I INVENTOR FREDERICKSODDY, OF GLASGOW, SCOTLAND MEANS AND APPARATUS FOR PRODUCING- HIGEVACUUMS.

Specification of Letters Patent.

Patented July 2, 1907.

Application filed July 13, 1906. Serial llo- 326,169

of the mercury pump, but of a degree of rarefaction I fully equal tothat which can be produced by the mercury pump under the most favorableconditions.

The process employed depends on the absorption by highly heated reagentsof the gases remaining after preliminary exhaustion by means ofmechanical air pumps or any other means. In the production of high vacuanot only has the air to be. removed but also the gases occluded orcondensed on the walls of th vessel being exhausted and on the containedelectrodes or filaments or other contents of the said vessel, whichcondensed gases are given up slowly after exhaustion and if not removedduring the exhaustion cause the vacuum to deteriorate.

I have discovered that certain reagents, hereinafter described, will actas rapid absorbents of almost all gases when heated to a hightemperature. This temterature is above that at which exhausted glassvessels soften and collapse, and as glass is the only material that canbe economically and satisfactorily employed for the containing vesselsin cases where the highest vacuum is desired, I have inverted means forheating the reagents in exhausted vessels made entirely of glass to ahigher temperature than the melting point of glass for the purpose ofproducing high vacua in the manner before described. Vessels ofporcelain or quartz are expensive and unreliable since they are apt tobecome porous in use, and they cannot be joined to the vessel to beexhausted and sealed therefrom after exhaustion by means of-the blowpipein the same way as glass vessels, and metal wires for carrying anelectric current cannot be sealed air tightly into any othermaterialexcept glass. Metal vessels cannot be employed in the production of highvacua for even if these are constructed entirely without joints orflawsof any kind, and are perfectlyair-tight the gases condensed in the metaland evolved from it in vacua prevent a high vacuum being readilyobtained therein. By m i vention I .have overcome the diificulty of theglass vessel collapsing at the high temperature employed, and by the useof glass vessels I can produce high vacua in a practicalmanner by meansof reagents which do not act as absorbents of gases below the softeningtemperature of glass.

One of the reagents I may employis-the metal calcium. I have discoveredthat the metal calcium under suitable conditions absorbs rapidly andcompletely nearly all gases, including not only oxygen and nitrogen thetwo chief constituents of atmospheric air but also hydrogen, carbondioxid, carbon monoxid, water vapor, acetylene, ammonia, sulfur dioxid,and even such a complex mixture as coal gas. The aforemen tionedcondensed gases consist chiefly of compounds of hydrogen carbon andoxygen and are readily and completely absorbed by metal calcium. Butmetal calcium will not entirely absorb atmospheric air, for it will notabsorb the argon which is present in air to the extent of about one percent, nor while it is in the highly heated condition will it completelyretain hydrogeii. The metal calcium instead .of being used alone may ifdesired be used in the form of alloys with other metal or metals, forexample with magnesium,

and I include in the term metal calcium alloys, conmetal calcium in theproduction of high vacua, and inthe following description it is to beunderstood that the metals barium and strontium or alloyscontainingthese metals as aforesaid can be employed, and all these are to beunderstood to be included where metal calcium is mentioned.

I have devised a method whereby metal calcium can be used in theproduction of highvacua, which method consists in first removing thewhole of the atmospheric air from the vessel being exhausted andafterwards employing heated metal calcium, to absorb the remaininggases, including the aforesaid gaseaafter they have been expelled fromthe walls, or walls and contents, of the vessel while subjected to heat.The removal of the I have also discovered that the Whole of theatmospheric air may be effected by replacement of the air with such gas,or gases, as is, or are, completely absorbed by heated metal calcium,either previously to, or during preliminary exhaustion.

The heating and expelling of the condensed and occluded gases may beeffected in any usual, or suitable, manner of expelling condensed andoccluded gases from the walls and contents of vessels being exhausted.The usual manner of effecting such an operation is to heat the vesselwhile it and its contents are subjected to the same treatment as theyare subjected to in after use. In incandescent electric'lamps forexample an electric current is passed through the filament, and in X raybulbs an electric discharge is passed between the electrodes during thecontinuation of the exhaustion.

The economical and rapid production of high vacua according to myinvention can be effected as follows In communication with .the vesselto be exhausted I place a receptacle for metal calcium, the saidreceptacle being provided with means for heating such metal calciumsufliciently to. volatilize it, in the manner heated metal calcium, andI first put the exhauster in communication vgzith the vessel andreceptacles and exhaust, as far as i's ipossible by this means, air fromthe vessel and receptacles, and then Ishut off the exhauster andgenerate the gas capable of being entirely absorbed by heated metalcalcium as aforesaid, and I again exhaust by means of the exhauster,repeating this supply .of such gas and exhaustion as may be necessary toreplace and remove all the air, and consequently all the argon. I thenshut off the vessel being exhausted and the receptacle containing themetal calcium from the exhauster and the receptacle containing the gasgenerating substance and keep. the vessel and its contents heated andsubjected to such treatment as hereinbefore indicated as will expel allcondensed, and occluded, gases from the walls and contents of the saidvessel, and 1 heat to the temperature at whichi it commences tovolatilize the metal calcium which then absorbs all remaining gasesandalso the gases expelled as aforesaid. Instead of using a specialsubstance to generate a gas, as aforesaid, for use in removing the airremaining after the preliminary exhaustioml the preliminary exhaus tionmay be continued while the vessel and its contents are subjected to suchtreatinent as hereinbefore indicated as will expel the condensed andoccluded- -'gases, and the gases expelled from the vessels and contentsof the said vessel be utilized instead of gases generated from a specialsubstance as aforesaid, this being possible, for instance in the'cas eof vessels and contents not previously exhausted. I I

Commercial samples of metal calcium give 0E gases, consisting mainly ofhydrogen, carbon, and oxygen, when heated in a vacuum to a temperaturebelow that at which these gases are absorbed by metal calcium, but thesegases are reabsorbed on raising the tempera: ture of the metal calcium.Use may be made of the gases evolved from metal calcium, in this way toassist in the replacement of the. air remaining in the apparatus in themanner before described. This is possible in the case of a new charge ofcalcium not previously heated in a vacuum. I

' When the metal calcium has absorbed the remainder of the gases whichhave been expelled, the exhausted vessel may besealed off and a veryhigh and permanent vacuum has been obtained in a rapid and economicalmanner. Towards the end of the process of absorption of the gases by themetal calcium the temperature of the metal calcium can, with advantage,be reduced, for I have found that certain of the compounds formed by thecombination of metal calcium;

with the gases it absorbs (and particularly the compounds with hydrogenand with carbon) possess an appreciable tension of dissociation attemperature, but that on sufiiciently lowering the temperature esaoai beexhausted, for example, an X ray bulb, B is the receptacle in which isthe container of the metal calcium 0, means being provided as at c, forheating it electrically to a high temperature as hereinafter described;D is the receptacle containing a substance which will furnish gas, orgases, capable of being entirely absorbed by metal calcium. Thisreceptacle D may be, for example, a glass tube containing a mixture of,say, potassium chlorate and manganese dioxid furnishing oxygen onwarming. E is the glass tube connected tothe exhauster, not shown. F isa tap to open and close communication with the exhauster, and G is a tapto open and close communication with the receptacle 1). H is a spectrumtube which may be of the usual kind and is a convenience for determiningby means of the spectroscope the nature of the re sidua l. gases in thevessel undergoing exhaustion.

I will now describe constructions of apparatus suitable for use incarrying out that part of my invention which relates to the heating ofthe reagent to a high temperature in a glass containing vessel, for thepurpose of causing it to absorb the remaining gases and so produce ahigh vacuum. For this purpose I employ, in combination with electricalmeans, as hereinafter described, for supplying heat to the reagentwithin glass vessel from softening, or melting.

As the glass vessel is partially, or completely, exhausted, theconduction of heat from within outward to the walls is much diminishedand in some cases I also interpose a shield, or shields, of refractorymaterial between the reagent being heated in the said vessel and thewalls of the said vessel to intercept heat- .radiated. The electricalheating is obtained by conduction of an electric current through aseparate resistance circuit placed within the said exhausted glass glassvessel and causing induced electrical effect through the walls of thesaid glass vessel, either in a circuit composed of the reagent to beheated or in a in close proximity to the reagent. For example, in onemodification of my apparatus I employ a combina-. ,tion of an exhaustedglass vessel with an electrical resistance circuit within the said glassvessel and surrounding the reagent to be heated and a shield, or Ishields, of refractory material placed between "the said resistancecircuit and the walls of the glass vessel, and in another modification Iemploy a combination of an exhausted glass vessel with a core of ironwires, or strips, inside the said vessel, and I dispose around the orintermittent, current of high periodicity, and I place around the core aring, or tube, composed of a good conductor of electricity in whichthe-heating current is induced. ring, or tube, may, in some cases 1 forexample in the case of metal calcium be made of the reagent to be.heated, or of a separate substance on,

' addition I may use with this combination arfl shields, of refractorymaterial which, in h case, m be an insulator of electricity, between thesubstance heated and the walls of the glass vessel, and also Inlay use ashield between the substance heated and the iron core. When the-heatingcurrentis induced directly in outside of the vessel a coil traversed byan alternating,

or in, which the reagent to be heated is placed. In

the glass vessel, means for protecting the walls of the vessel, or byelectrical means situated outside the said separate circuit within thesaid exhausted glass vessel the substance to be heated, this substanceis hotter than its surroundings, so that less heat is required than forany other mode of heating and the glass vessel needs less protection inthis case and the shield, or shields,

*1 core within it.

' being respectively sections on the lines-2;, y and 2, Fig. 10

2. Figs. (Sand 7 show a form of the apparatus according to the secondmentioned modification. Figs. 8 to 12 represent another modification ashereinafter described.

Referring firs t to Figs. 2 to 5. The glass vessel Bis closed by a glasstube B ground into the vessel B, and

having two hollow legs, or pockets, 1;, filled with mercury into whichpenetrate the platinum conductorsb from the respective poles of anysuitable source of electricity. I- is a porcelain insulator throughlongitudinal celain shield-tube K; Inside the tube J is carried theporcelain container L for the reagent 0, which is to be heated. Theupper enlarged part is employed when a reagent such as metal calcium isused which gives off a vapor which it is desirable to condense thisenlarged part constituting a surface upon which the vaporized reagentwill deposit. The shield-tube K serves to protect the glass of thevessel B from the heat radiated from the resistance wire L2. If desiredthere may be more than one shield-tube of refractory and insulatingmaterial between the substance to be heated and the glass vessel B, orthe glass vessel may be formed into a bulb at the part where thegreatest heat is developed.

, Reiering to the modification shown in Figs. 6 and 7, this shows anarrangement adapted for use when the reagent, for example, metalcalcium, is itself a conductor of electricity and canbe made intosuitable form. The substance to be heated is made into the form of aring, or tube, ,0, which may be supported in a tube K constituting ashield of refractory and insulating material, in the glass vessel B.Within the substance 0 and i this tube K are iron wires, or strips, Marranged after the manner oi the core of an induction coil and containedin the tube 1 of thin glass, or porcelain. The ring, or tube, C'isheated by an electric current induced in it either by a bobbin ofinsulated wire, or by spiral strips, as shown at N, traversed by analternating, or inter- 'mittent, current of high periodicity and coiledoutside the glass vessel B and therefore surrounding the iron Thisheating arrangement constitutes an" alternate, or intermittent, currenttransformer of i which the outside coilings N constitutethe primary, thering, or tube, G'the single short-circuited winding of-the secondary,and the iron wires, or.strips, M the core. It may be convenient toobtain the alternating, or intermittent, current from a step-downtransformer (not shown) of which N is the secondary and C is the -may,in some cases, be dispensed with as explained, and the outer glass tubeat this part be expanded into a bulb, and the coreM be made longer andthe spiral N be placed above, or below, the bulbs The ring 0 in thiscase is conveniently supported on a projection on the tub K. When it isdesirable to protect or inclose'the core M the. said core may, as shown,be contained in a sealed tube P of diflicultly fusible glass, which, ifnecessary, may beprotected externally by wrapping round it a sheet ofmica, or other refractory material, or by placing round it a concentricshield of porcelain. With this method of heating, the limitation oftemperature .is fixed mainly by the loss of the magnetic properties ofthe iron core above a certain temperature, so that for very hightemperatures the iron as well as the glass walls must be shielded. Forthe purpose of charging and cleaning the apparatus, the glass vessel Bmay, if desired, be made in two, or more, parts ground to fit togetheraccurately without leakage when the ground joint is lubricated withrubber grease in the usual manner.

Fig. 8 represents a scale modification of the apparatus for use in theinductive method of heating upon the same principle as that lastdescribed. Fig. 9 is a section actual size ofapart of the apparatus.Fig. 10 is a central transverse section; Fig. 11 asection at rightangles thereto and Fig. 12 a' horizontal section. The" reagent, forexample, metal calcium, is in the form of a disk 0 with a central holethrough which a magnetic material such as a bundle of iron wires, orstrips, M, passes the said wires, or strips, supporting the disk C,centrally, in the glass vessel B. Outside the glass vesselgB is amagnetic material such as a bundle of iron wires, or strips, M bent intoapproximately ring form and so arranged that it forms, with the ironwires, br strips, M, or the equivalent, inside the glass vessel B amagnetic circuit with two air gaps in which part of the walls of theglass vessel B are situated. A conductorN. of copper, or other suitablemetal, is coiled around the outer wires, or strips, M and through thisis passed a rapidly alternating, or intermittent, electric current so asto induce a magnetic flux in the magnetic ring and consequently in thebundle of wires, or strips, M, or the equivalent,

within the glass vessel B, and so heat the disk 0.

The disk Q if desired be made of a good conductor, for example,copper,-and the reagent heated in a cavity in the same. Or, two disks ofcopper and a disk of the reagent placed between the other two disks maybe employed. The drawing shows two caps, or shields, P of porcelain, orother sufficiently refractory material which is a bad conductor of heat,these caps, or shields, being used to protect the walls of the glassvessel B from the heat generated in the disk 0. Having now particularlydescribed and ascertained the nature of my said invention and in whatmanner .the same is to be perfor'med, I declare that what permittingsaid metal. to cool, substantially as described.

5. Apparatus for the purpose of producing high vacuum by heating in anexhausted glass vessel to a temperature above the softening point. ofglass any reagent which becomes an absorbent of gases at hightemperature, the said apparatus consisting of the combination of a glassvessel adapted to be exhausted, means for supporting therein the reagentand means for electrically heating such reagent within the vacuum andmeans for ,pre-

venting the intense heat being conveyed to the walls of eesgosi the saidglass vessel, substantially as hereinbefore described.

6. Apparatus for the purpose of producing high vacuu by heating in anexhausted glass vessel to a temperature above the softening point ofglass any reagent which becomes an absorbent of gases at hightemperature, the said apparatus consisting of the combination of a glassvessel adapted to be'exhausted, 'means for supporting therein thereagent to be heated and means for heating such reagent within thevacuum by means of an electric current passing through a "conductorexternal to the glass vessel and inductively heating the aforesaidreagent by current, and means for preventing the intense heat being"conveyed to the walls of the glass vessel, substantially ashereinbefore described.

In testimony whereof I have signed this specification in the presence oftwo subscribing witnesses.

FREDERICK sonpr.

Witnesses:

THOMAS D; MACKENZIE,

ARTHUR J.' BERRY.

